Just after the first of the year, the folks at Stoner Car Care asked if I’d like to test their Invisible Glass Clean & Repel together with the company’s Invisible Glass Washer Fluid Additive. This combination, it’s claimed, is simple to use, minimizes the time spent treating the windows (a good thing in cold temps), improves visibility in inclement weather, and lasts for weeks. With February, usually a dull gray month filled with snow and slush, right around the corner, I agreed to the test.

For ages I have used Rain-X on my windows, enjoying its ability to make water bead up and roll off the windows. What I didn’t like about that product, however, was the need to scrupulously clean the windows before applying the liquid. (I often found it necessary to scrub the windshield with Bon Ami cleanser and thoroughly rinse the surface with water in order to remove the thin film of rubber and grit left behind by the wiper blades to get the best result.) And application is neither easy nor simple. Rain-X has to be applied in overlapping circles, allowed to haze over, and then buffed off. Even then you’ll often end up with a haze that requires wiping a slightly damp cloth lightly across the surface, and drying the window with another clean cloth. But the result was spectacular, with rain zipping across the windshield for a few days or so before the effect began to diminish.

Unfortunately for my test regimen, February turned out to be warmer and dryer than normal, with very little snow. So much for testing the Stoner products in slush and snow. Rain would have to suffice. However, I decided to forge ahead, cleaning the windows one side of my car with the Invisible Glass Clean & Repel, and the other with normal Invisible Glass. This wasn’t as easy as it sounds since overspray from the Clean & Repel side contaminated the other side of the windshield, necessitating a second cleaning with Invisible Glass. Also, using a cloth from the Clean & Repel side to absentmindedly wipe a spot off a non-treated window was enough to leave a thin film of repellant on that window that required removal for this test.

Once the windows were cleaned, I filled the windshield washer reservoir with the recommended amount of the washer fuid additive, drove the car for a couple of miles to mix things up, and sprayed the windshield. I was ready for whatever Mother Nature had to throw at me over the next few weeks.

That turned out to be alternating days of sunshine and rain (sometime torrential), and the occasional snowflake. It was not the sloppy, wet, slushy mess February usually brings. Nevertheless, the difference between the treated and untreated surfaces was noticeable. The water beaded up faster and ran off more easily on the surfaces treated with the Clean & Repel, though it didn’t reach the seemingly friction-free state of windows freshly treated with Rain-X. However, though the effect wasn't as stark, the repellency of the surfaces treated with Clean & Repel lasted much longer and was more consistent throughout that period. And it could be brought back with a simple spray and wipe, if necessary. Even more impressive was the combination of Clean & Repel and Invisible Glass Washer Fluid Additive on the windshield. Though the additive placed a repellent film on both the treated and untreated sides, the wipers on the Clean & Repel side had less drag and did a better job of cleaning the surface. And though water droplets didn’t fly off the windshield at speed, as they would have for a short time with a fresh application of Rain-X, as the wipers gathered the rain in their path, this larger sheet of water would flow smoothly across the surface and away from my field of vision. Plus, it would continue to do so for a long period of time. Weeks would pass, and the repellency would diminish only slightly, avoiding the drop off a cliff that happens with Rain-X.

The bottom-line is this: If you use Invisible Glass Clean & Repel in combination with Stoner’s Invisible Glass Washer Fluid Additive, expecting the sheeting effect you get from an initial Rain-X application, you may be disappointed. The water will not bead up and run off in the same manner. However, you also will discover that, though the initial effect is not as dramatic as it is for Rain-X, the repellency of the Stoner products lasts longer, and reduces the drag of the wipers across the windshield. Follow-up applications are simpler, easier, and reduce the time and effort spent; a big plus in winter weather or when time is at a premium.